Endless metal ring manufacturing method and endless metal ring resin removal device

ABSTRACT

Provided is an endless metal ring manufacturing method for manufacturing an endless metal ring by carrying out a barrel polishing step for polishing the endless metal ring by using a barrel of a resin material, a rolling step for rolling the endless metal ring which was cleaned, and a nitriding step for nitriding the endless metal ring which was rolled, wherein after the barrel polishing step and before the rolling step, provided is a resin removing step for removing resin that has adhered to the endless metal ring.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 14/765,185filed Jul. 31, 2015, the entire contents of which is incorporated hereinby reference. U.S. application Ser. No. 14/765,185 is a 371 ofInternational Application No. PCT/JP2013/063260 filed May 13, 2013.

TECHNICAL FIELD

The present invention relates to a method of manufacturing an endlessmetal ring for constituting a laminated ring mounted in a CVT belt, andrelates to a technique of preventing generation of nitriding failureduring manufacturing of the endless metal ring by improving a washingprocess and a washing method.

BACKGROUND ART

In recent years, there have been increased vehicles provided with acontinuously variable transmission (CVT). By loading a CVT in a vehicle,a gear ratio on an engine output side can be controlled in a steplessmanner, and fuel efficiency of a vehicle is enhanced. This is becausestepless controlling of the gear ratio by the CVT can efficiently deriveor produce engine power. The CVT is formed by a combination of laminatedendless metal belts and a plurality of elements and the CVT is woundaround an input side pulley and an output side pulley to transmit power.The input side pulley and the output side pulley are each provided witha pair of sheaves which steplessly can change each groove width betweeneach pair of the sheaves, and thereby the input side pulley and theoutput side pulley can continuously change rotation ratios, i.e., gearratio, at an input side and an output side in a stepless manner byvarying the groove widths.

Because of the above-mentioned configuration of the CVT, an endlessmetal belt and an element used for the CVT are required to have highlyprecise dimension. Engine output is transmitted to the endless metalbelt and the element, and therefore the endless metal belt and theelement are repeatedly subject to an amount of load corresponding toengine operation. In view of strength and life expectancy, it has beenavoided to mount the CVT in a vehicle with a high-power engine.

Patent Document 1 discloses a technique relating to a hoop for a CVTbelt and a manufacturing method therefor. In polishing a hoop (anendless metal ring) for a CVT belt, barrel polishing is conducted usingmedia made by mixing abrasive grains and a binder on condition that theabrasive grains are oxide-type and bulk specific gravity of the media isequal to or less than 2.0 or on condition that the abrasive grains arecarbide-type and the bulk specific gravity of the media is equal to orless than 1.6. Accordingly, a size of foreign matter to be driven intothe hoop is restricted.

Patent Document 2 discloses a technique relating to a manufacturingapparatus and a manufacturing method for an endless metal ring used fora continuously variable transmission. A polishing device for the endlessmetal ring includes an end face polishing device and an inner and outercircumferential surface polishing device. The inner and outercircumferential surface polishing device includes: a ring rotationroller for rotating the endless metal ring; an outer circumferentialsurface polishing roller to be brought in contact with an outercircumferential surface of the endless metal ring; an innercircumferential surface polishing roller to be brought in contact withan inner circumferential surface of the endless metal ring; and aconstant-pressure applying actuator for moving the outer circumferentialsurface polishing roller and an inner circumferential side backup rollerto change a clearance therebetween and surface pressures thereof and formoving the inner circumferential surface polishing roller and an outercircumferential side backup roller to change a clearance therebetweenand surface pressures thereof. Owing to this configuration, it ispossible to prevent unevenness in film pressure of nitride films to beformed on an endless metal ring surface by nitriding.

Patent Document 3 discloses a technique relating to a manufacturingmethod for a steel belt. This is a method for manufacturing a steel beltfrom a sheet material made of high-tensile steel. The method includes: amultiple deep drawing step in which a sheet material made ofhigh-tensile steel is subjected to deep drawing and further to anotherdeep drawing at least once or more at a different drawing ratio from theformer drawing; and a cutting step in which an element processed in themultiple deep drawing step is circumferentially cut into a belt-likeshape. According to this method, a steel belt with high strength can bemanufactured without performing welding operation.

RELATED ART DOCUMENTS Patent Documents

-   Patent Document 1: JP-A-2003-049906-   Patent Document 2: JP-A-2005-155755-   Patent Document 3: JP-A-2007-152358

SUMMARY OF INVENTION Problems to be Solved by the Invention

Accompanied with progress in a CVT technology, there has been a demandfor adapting CVTs to a high-powered engine, and enhancing lifeexpectancy and endurance of a CVT belt has also been expected. However,when an endless metal ring to be used for a CVT belt is manufactured byusing the technology disclosed in Patent Documents 1 to 3, thosetechniques have the following problems.

For forming an endless metal ring, every one of the Patent Documents 1to 3 requires a cutting process and a cylindrically shaped element hasto be cut with a predetermined width to make an endless metal ring. Incutting, burrs could be generated in any cutting methods, and thereforeit is necessary to provide a process to remove thus generated burrs. Ina method shown in the Patent Document 2, a removal process has to beperformed for the endless metal rings one by one, requiring a longprocessing time, which could induce a cost problem. Accordingly, thepresent applicant employed a method of removing burrs from an endlessmetal ring by barrel polishing as indicated in the Patent Documents 1and 3. However, it is confirmed that nitriding failure occurs with acertain probability when the endless metal ring is subjected to surfacetreatment by rolling and nitriding after the barrel polishing. Due tothis nitriding failure of the endless metal ring, it is assumed thatlife expectancy and endurance of a CVT belt lower.

The present invention has been made in view of the circumstances tosolve the above problem and has a purpose to provide an endless metalring manufacturing method and an endless metal ring resin removal devicewhich are capable of lowering a rate of nitriding failure of the endlessmetal ring.

Means of Solving the Problems

To achieve the above purpose, an endless metal ring manufacturing methodaccording to one aspect of the present invention has the followingfeatures.

(1) One aspect of the invention provides an endless metal ringmanufacturing method including: a barrel polishing step of polishing anendless metal ring by use of a barrel made of resin; a rolling step ofrolling the endless metal ring having been washed; and a nitriding stepof nitriding the rolled endless metal ring, wherein the manufacturingmethod further includes a resin removal step of removing the resin thathas adhered to the endless metal ring.

According to the aspect described in the above (1), it is possible tolower the rate of nitriding failure of the endless metal ring. Theapplicant made a research with various washing conditions for theendless metal ring in nitriding the endless metal ring. As a result ofthe research, it is confirmed that there is a problem in removing themedia used for barrel polishing. To be specific, the media is made bymixing resin material and polishing material, and the applicant hasconfirmed from the research result that the nitriding failure occursbecause the nitriding is performed in a state that the resin materialstays on a metal surface. The resin adhered to the metal surfaceobstructs nitrogen molecules from entering into the metal from the metalsurface in the nitriding step, resulting in thinning a thickness of anitrogen diffusion layer, so that the metal could be formed withportions with low surface strength in a mottled appearance. This is thenitriding failure to cause a product failure. Accordingly, by removingthis resin extraneous matter, it is possible to reduce the nitridingfailure of the endless metal ring.

(2) In the endless metal ring manufacturing method according to (1),preferably, the resin removal step is performed after the barrelpolishing step and before the rolling step.

It is confirmed that it is effective to remove the resin extraneousmatter adhered to the surface of the endless metal ring before therolling step in order to lower the nitriding failure of the endlessmetal ring. If the resin remains to adhere to the surface of the endlessmetal ring before the rolling step, the resin could be fixed or stick tothe surface of the endless metal ring in the rolling step, andexfoliation of the resin becomes extremely difficult even if the endlessmetal ring surface is thoroughly washed after the rolling step.Therefore, by removing the resin before the rolling step, fixation ofthe resin to the endless metal ring surface is prevented, and therebythe nitriding failure can be prevented.

(3) In the endless metal ring manufacturing method according to (1) or(2), preferably, the resin removal step includes soaking the endlessmetal ring in a decomposition treatment liquid to remove the resin.

According to the aspect described in the above (3), the resin adhered tothe endless metal ring is fused to be removed by use of thedecomposition treatment liquid and the rolling step is subsequentlyperformed, so that the resin is prevented from being fixed to theendless metal ring surface, resulting in prevention of the nitridingfailure.

(4) In the endless metal ring manufacturing method according to (1) or(2), preferably, the resin removal step includes causing a fluid tocollide against a surface of the endless metal ring to remove the resin.

According to the aspect described in the above (4), a fluid is caused tocollide against the endless metal ring surface by a large flow ratewashing, for example, to remove the resin, and the rolling step issubsequently performed, so that the resin is prevented from being fixedto the endless metal ring surface, resulting in prevention of thenitriding failure.

(5) In the endless metal ring manufacturing method according to (1) or(2), preferably, the resin removal step includes soaking the endlessmetal ring into a liquid to perform ultrasonic washing.

According to the aspect described in the above (5), the endless metalring surface is subjected to the ultrasonic washing to remove the resinand the rolling step is subsequently performed, so that the resin isprevented from being fixed to the endless metal ring surface, resultingin prevention of the nitriding failure.

(6) In the endless metal ring manufacturing method according to (5),preferably, the resin removal step includes rotating the endless metalring to wash the endless metal ring.

According to the aspect described in the above (6), the endless metalring is rotated during the ultrasonic washing in order to change alocation of ultrasonic wave irradiated on the endless metal ringsurface, and as a result, a location of cavitation generated on theendless metal ring surface is changed. Accordingly, it is possible tofacilitate exfoliation of the resin from the endless metal ring surface.In this manner, it is possible to prevent the resin from being fixed tothe endless metal ring surface, resulting in prevention of the nitridingfailure.

Further, to achieve the above purpose, an endless metal ring resinremoval device according to another aspect of the present invention hasthe following features.

(7) Another aspect of the present invention provides an endless metalring resin removal device configured to wash and hold an endless metalring, wherein the endless metal ring resin removal device includes: aholding tool for holding the endless metal ring; a rotation mechanismconfigured to rotate the endless metal ring in a circumferentialdirection of the endless metal ring with the holding tool; a washingtank filled with a liquid for ultrasonic washing of the endless metalring; and an ultrasonic wave generator for performing the ultrasonicwashing.

(8) In the endless metal ring resin removal device according to (7),preferably, the ultrasonic wave generator is operated while the rotationmechanism rotates the endless metal ring in the circumferentialdirection to remove resin having adhered to a surface of the endlessmetal ring.

According to the aspects described in the above (7) and (8), the endlessmetal ring is washed while the ring is rotated, so that the resinadhered to the endless metal ring surface can be effectively removed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a CVT ring in a first embodiment;

FIG. 2 is an exploded perspective view of the CVT ring in the firstembodiment;

FIG. 3 is an explanatory view explaining a manufacturing process of anendless metal ring in the first embodiment, in which (a) is a stripcutting step, (b) is a strip welding step, (c) is a first solutionizingstep, (d) is a cylindrical body cutting step, (e) is a barrel polishingstep, (0 is a washing step, (g) is a rolling step, (h) is a secondsolutionizing step, (i) is a circumferential length adjusting step, (j)is an aging and nitriding step, and (k) is a laminating step;

FIG. 4 is a diagram showing a carbo-nitriding mechanism in the firstembodiment, in which (a) is an ammonia gas charging step, (b) is anitrogen adsorption step, (c) is an ammonia dissolution step, (d) is anitrogen infiltration step, and (e) is a nitrogen diffusion step;

FIG. 5 is a schematic view of a washing device in the first embodiment;

FIG. 6 is a perspective view of a washing jig in the first embodiment;

FIG. 7 is a diagram showing a first model of nitriding failure forexplanation;

FIG. 8 is a diagram showing a second model of nitriding failure forexplanation;

FIG. 9 is a schematic view of a configuration of a six-tank washing forexplanation;

FIG. 10 is a graph showing results of resin removal tests conducted bythe applicant;

FIG. 11 is a perspective view of a washing jig for explanation;

FIG. 12 is a schematic plan view of a washing device in a secondembodiment;

FIG. 13 is a schematic perspective view of the washing device in thesecond embodiment;

FIG. 14 is a perspective view showing an image of washing an endlessmetal ring in a third embodiment; and

FIG. 15 is a table showing washing results of the endless metal ring inthe first embodiment.

MODE FOR CARRYING OUT THE INVENTION

A first embodiment of the present invention is now explained referringto the accompanying drawings.

FIG. 1 is a perspective view of a CVT ring 100 in the first embodiment.FIG. 2 is an exploded perspective view of the CVT ring 100. The CVT ring100 is formed of a laminated ring 104 and a plurality of elements 102stacked in a thickness direction thereof. The laminated ring 104 isformed by laminating nine layers of endless metal rings 110, each layerhaving the different circumferential length. In FIG. 2, the endlessmetal rings 110 are omitted partly and illustrated by only three layersthereof for explanation. The adjacent endless metal rings 110 are eachdesigned to have different inner diameters by the thickness of eachendless metal ring 110. Accordingly, the overlapped endless metal rings110 are laminated with no clearance. The elements 102 are each made ofplate-like metal material formed at both ends with grooves 116, and thelaminated rings 104 are inserted in these grooves 116 as shown in FIG.2.

FIG. 3 is a schematic view for explaining a manufacturing process forthe endless metal ring 110. In FIG. 3, (a) is a strip cutting step pr1,(b) is a strip welding step pr2, (c) is a first solutionizing step pr3,(d) is a cylindrical body cutting step pr4, (e) is a barrel polishingstep pr5, (f) is a resin removal step pr6, (g) is a rolling step pr7,(h) is a second solutionizing step pr8, (i) is a circumferential lengthadjusting step pr9, (j) is an aging-nitriding step pr10, and (k) is alaminating step pr11. For manufacturing the endless metal ring 110, asshown in FIG. 3(a), a strip plate P2 is cut out from a material roll P1to a specified length in the strip cutting step pr1. High-tensile steelsuch as maraging steel is used for the material roll P1. This materialroll P1 is uncoiled to be flattened, and then cut with a predeterminedwidth to form the strip plate P2. The width of the strip plate P2 isdetermined in consideration of being subject to subsequent process suchas the rolling step pr7.

Then, in the strip welding step pr2 shown in FIG. 3(b), a cylindricalbody C1 formed by roll-bending the strip plate P2 is welded by abuttingits end faces to form the cylindrical body C1 of cylindrical shape. Inthe first solutionizing step pr3 shown in FIG. 3(c), the cylindricalbody C1 is solutionized under nitride atmosphere. By this solutionizing,structure anisotropy of the welded portion is relaxed. In thecylindrical body cutting step pr4 shown in FIG. 3(d), the cylindricalbody C1 is cut into round slices each having a predetermined width tomake a material ring C2. Since burrs are generated on end faces of thematerial ring C2 in the process of cutting the cylindrical body C2 intoround slices, the barrel polishing step pr5 shown in FIG. 3(e) isperformed to remove the burrs generated on the end faces of the materialring C2. What is used in the barrel polishing step pr5 is resin media inwhich alumina abrasive grain with a prescribed grain diameter is mixedwith a resin-based binder.

Then, in the resin removal step pr6 shown in FIG. 3(f), the materialring C2 after barrel polishing is cleaned. This resin removal step pr6will be explained later. In the rolling step pr7 shown in FIG. 3(g), athickness of the material ring C2 is adjusted. Even though the materialroll P1 is provided to have a thickness as uniform as possible, therolling step pr7 of rolling the material ring C2 by use of rollingrollers R1 is performed in order to correct a deviation in the thicknessdirection, thickness variation and minute deformation in the stripwelding step pr2 and the cylindrical body cutting step pr4, andinfluence in the barrel polishing step pr5. A rolled ring C3 formed inthis step has a thickness set assuming that a circumferential length isto be elongated in the subsequent circumferential length adjusting steppr9.

In the second solutionizing step pr8 indicated in FIG. 3(h), the rolledring C3 is heated in a furnace at a predetermined temperature for apredetermined period of time. This solutionizing process is aimed forhomogenization. In the circumferential length adjusting step pr9 shownin FIG. 3(i), each of the rolled rings C3 is adjusted to a requiredcircumferential length, and then the endless metal ring 110 is formed.Then, a carbo-nitriding treatment is performed in the aging-nitridingstep pr10 indicated in FIG. 3(j). FIG. 4 is a diagram showing acarbo-nitriding mechanism. In FIG. 4, (a) is an ammonia gas chargingstep, (b) is a nitrogen adsorption step, (c) is an ammonia dissolutionstep, (d) is a nitrogen infiltration step, and (e) is a nitrogendiffusion step. The endless metal ring 110 set in a not-shownpressure-reduced furnace is placed under ammonia gas atmosphere in “theammonia gas charging step” in FIG. 4(a).

When the temperature in the furnace is raised after that, ammoniamolecules adhere to a surface of the endless metal ring 110 in “thenitrogen adsorption step” in FIG. 4(b). Then, as shown in “the nitrogendissolution step” in FIG. 4(c), the ammonia molecules dissolved on thesurface of the endless metal ring 110 are decomposed to nitrogen andhydrogen. The nitrogen reacts with minute particles in the endless metalring 110 and then enters into the endless metal ring 110 from itssurface as indicated in “the nitrogen infiltration step” in FIG. 4(d).This reaction occurs because of the influence of components that havehigh affinity with nitrogen among elements included in the steelmaterial. The nitrogen is diffused mainly from a grain boundary of theendless metal ring 110 in “the nitrogen diffusion step” in FIG. 4(e),and as a result, the effect of hardening the surface of the endlessmetal ring 110 is obtained.

Thus formulated endless metal rings 110 are laminated in the laminatingstep pr11 shown in FIG. 3(k). In the first embodiment, the endless metalrings 110 are laminated in nine layers to form the laminated ring 104.The thus laminated ring 104 is utilized to form the CVT ring 100 bycombination with the elements 102 as shown in FIG. 2.

FIG. 5 is a schematic view showing a washing device 10. FIG. 6 is aperspective view showing a washing jig 20. The washing device 10 used inthe resin removal step pr6 is configured such that the washing jig 20shown in FIG. 6 is held in a rotatable manner in a washing tank 40filled with water for washing, and an ultrasonic wave generator 30 isplaced below the washing jig 20. The washing jig 20 is a basket made ofthin wire to hold the material rings C2 as shown in FIG. 6, and thewashing jig 20 is covered with an unillustrated lid and fixed in thewashing device 10. The washing jig 20 provided in the washing device 10is provided with a not-shown rotation mechanism so that the jig 20rotates about an axis of the material ring C2. The ultrasonic wavegenerator 30 is placed to generate ultrasonic wave from below thewashing jig 20. In this manner, the material ring C2 after the barrelpolishing step pr5 is washed.

According to the above configuration of the manufacturing method of theendless metal ring 110 in the first embodiment, the following operationsand effects are obtained.

The method of manufacturing the endless metal ring 110 in the firstembodiment is the method for manufacturing the endless metal ring 110through the process of: the barrel polishing step pr5 of polishing thematerial ring C2 (the endless metal ring 110) by use of a barrel made ofresin; the rolling step pr7 of rolling the washed material ring C2 (theendless metal ring 110); and the nitriding step pr10 of nitriding therolled ring C3 (the endless metal ring 110) which has been rolled. Themethod includes the resin removal step pr6 of removing the resin adheredto the material ring C2 (the endless metal ring 110) after the barrelpolishing step pr5 and before the rolling step pr7.

For manufacturing the endless metal ring 110, the applicant examined thesurface of the endless metal ring 110 after the nitriding step pr10 andconfirmed that the surface is shaded or mottled with black speckles orspecks and white speckles and that thus mottled portion is low in itshardness compared to other portions on the surface. Generally, nitrogenare diffused into the grain boundary from a surface layer of the endlessmetal ring 110 by “the nitrogen diffusion step” shown in FIG. 4(e) sothat a nitride layer r2 is formed. As a result, the surface of theendless metal ring 110 is hardened. However, the mottled portion withthe black and white speckles has low hardness and thus the nitridefailure is conceived to have occurred. This failure in the surfacehardness leads to product defect in the endless metal ring 110, loweringproduct yield. When the surface of the endless metal ring 110 isprocessed with shot peening as shown in FIG. 7(g) and FIG. 8(f) whichwill be mentioned later, the surface hardness failure further causesurface asperities.

Conventionally, some measures have been taken, for example, amanufacturing process is conducted in a clean room and humidity controlis performed for static electricity prevention in order to solve theabove problem. These measures are intended to prevent adhesion of dirtor wastes generated in the manufacturing process as much as possiblesince the nitriding failure has been considered to result from adhesionof the dirt or wastes to the surface of the endless metal ring 110 dueto static electricity.

However, even if the above measures are taken and the ring is carefullywashed in the washing process corresponding to the resin removal steppr6, the nitriding failure has occurred at a certain ratio. FIG. 9 is aschematic view showing a configuration of six-tank washing forcomparison. Conventionally, the endless metal ring 110 was carefullywashed through the six-tank washing process as shown in FIG. 9 after thebarrel polishing step pr5. Through the first to fourth tanks, theendless metal ring 110 is washed by the combination of ultrasonicwashing using pure water and oscillation. The endless metal ring 110 isthen washed with pure water in the fifth tank and applied with spin-dryto spin off drops of water by rotating the ring 110 at high speed in thesixth tank. Even by this washing method, it is hard to prevent thenitriding failure. Accordingly, the present applicant has analyzedforeign matters detected after washing by the six-tank washing andnoticed the fact that a large number of resin components are detectedfrom the foreign matters.

This resin component is considered to be mainly derived from the mediaused in the barrel polishing step pr5. Accordingly, in the firstembodiment, the resin removal step pr6 is performed before the rollingstep pr7 to wash the endless metal ring 110 by use of the washing device10 and the washing jig 20 shown in FIGS. 5 and 6. As a result, it isconfirmed that the resin can be preferably removed.

FIG. 7 is a diagram showing a first model having the nitriding failurecaused therein for explanation. In FIG. 7(a), washing failure causesemulsification of resin wastes, rolling oil, and compounds which aremixed with dust generated during the process and adhere to the surfaceof the endless metal ring 110. It is expected that this emulsifiedsubstance b1 turns into a carbon-based high polymer b2 in (b) indicatinga timing of the first solutionizing step pr3 and this polymer b2 sticksto the surface of the endless metal ring 110. Then, the carbon-basedhigh polymer b2 turns into a carbide substance b3 in an aging process(c). This carbide substance b3 obstructs creation of an iron oxide layerr1 which is to be formed on the surface of the endless metal ring 110 inan oxidizing process (d). Also when a nitride layer r2 is formed in anitriding process (e), the carbide substance b3 partly obstructscreation of the nitride layer r2 by interrupting carbo-nitridingindicated in FIG. 4(d). This obstruction is considered to cause theblack speckles on the endless metal ring 110 surface.

At that time, if the carbide substance b3 is peeled off due to somereasons as indicated in (0, it may lead to generation of the whitespeckles. The endless metal ring 110 formed in this manner could havethe low surface hardness due to the nitriding failure in portions of theblack speckles and the white speckles. Further, in a case that a shotpeening process is performed before the laminating process pr11thereafter, there are created partial unevenness as indicated in (g),which is not preferable.

FIG. 8 is a diagram showing a second model having the nitriding failureoccurred therein. Unlike the first model of the nitriding failure, noobvious reason to cause the failure is found, but an oxide layer r3 ofsuch as titanium is formed on the endless metal ring 110 surface in asolutionizing process (b), and this oxide layer has an influence ofobstructing creation of the iron oxide layer r1 as indicated in thefollowing (d). As a result, the nitriding failure indicated in (e) isconsidered to occur. Further, when the shot peening process is performedas indicated in (f), partial unevenness could be generated, which is notpreferable.

FIG. 10 is a graph showing results of resin removal tests in which thewashing device of the first embodiment is used under different washingconditions. The applicant has confirmed from the resin removal teststhat the washing device 10 can be applied to any one or the whole of thefirst to fourth tanks of the washing tank shown in FIG. 9, and that theefficiency in resin removal changes depending on the washing conditions.The graph of FIG. 10 is indicated with its vertical axis indicating apartial correlation coefficient and its horizontal axis indicating testconditions. The test results are obtained by further performingultrasonic washing with carbon tetrachloride solution, filtrating thesolution with a filter, and then evaluating a resin waste amount in thefilter after washing so that the grading is made.

“Ultrasonic power” is an element indicating an influence of anultrasonic power output w/L, and “Work set jig” is an element indicatingthe influence of using jigs different in shape, material, or the like.From the test results, it is confirmed that increasing energy per unitarea from 8 w/L to 24 w/L, could improve detergency by three ranks.

FIG. 11 shows a jig which has been conventionally used. A jig 21 made ofresin is configured with a thick frame with high rigidity compared tothe washing jig 20. Both the jig 21 and the washing jig 20 are capableof accommodating the same number of the endless metal rings 110. As for“Work set jig,” tests are made with the jig 21 shown in FIG. 11, thewashing jig 20, and without using a jig. What is the most effective inwashing is the case when the ring is washed without using any jig, andthe washing effect gradually becomes low in the order of using thewashing jig 20 and using the jig 21. This is because the high washingeffect is obtained when there is no jig which interrupts the ultrasonicwave.

“Rotation” is an element indicating an influence of performing or notperforming rotation by the washing jig 20. Compared to not performingthe rotation, washing with rotation exhibits higher washing effect byabout four ranks. “Air blow” is an element indicating an influence ofair blowing on the surface of the endless metal ring 110 after theultrasonic washing for comparison. It is confirmed that resin on theendless metal ring 110 surface is not removed by the air blow. “Numberof work sets” is an element indicating an influence of changing thenumber of the endless metal rings 110 accommodated in the washing jig20. It is confirmed that the washing effect is not largely influenced bythe number of the work sets.

“Temperature” is an element indicating an influence of the temperatureof a solution used for washing the endless metal ring 110. As a resultof tests made by changing the temperature from the room temperature inseveral different patterns, it is confirmed that the washing effect isimproved by raising the temperature to a certain degree. “Solution” isan element indicating an influence of types of the solution filled inthe washing tank 40 of the washing device 10. As the solution, purewater and hydrocarbon-related solution are used for the tests. Thesetests revealed that, compared to the pure water, the hydrocarbon-relatedsolution hardly makes the washing effects, and the hydrocarbon-relatedsolution is less effective by five ranks compared to the pure water.

As results from this research, as shown in FIG. 10, the elements of“Ultrasonic power,” “Work set jig,” “Rotation,” “Temperature,” and“Solution” have the partial correlation coefficient of more than 0.4,and it is concluded that they are effective. From these results, in thefirst embodiment, the washing jig 20 shown in FIG. 6 is employed as thework set jig to be rotated as shown in FIG. 4 so as to increase theultrasonic power, and water is employed as the solution so that thewashing effect of washing the resin dusts is further increased. Namely,the washing device 10 is thus arranged so that the resin dusts arefurther effectively removed from the endless metal ring 110 surface,realizing decrease in the nitriding failure of the endless metal ring110. The applicant has confirmed that by embodying the invention as thefirst embodiment, a nitriding failure ratio of the endless metal ring100 is reduced to almost zero while the ratio is used to be about 40%.Consequently, the present invention can attribute to cost reduction inproducing the endless metal ring 110.

FIG. 15 is a table showing that a rank of the washing effect varies inaccordance with test conditions. In a row indicated with “Comparativeexample,” the jig 21 shown in FIG. 11 is used and a result of thesix-tank washing illustrated in FIG. 9 in which the washing is performedwithout rotating the jig 21 is indicated. In the table, the steps in thefifth and sixth tanks are omitted. A row indicated as “Test 1” shows theresult of washing performed by the washing jig 20 shown in FIG. 6 whilethe jig 20 is rotated to wash the ring through the first to third tanks.A row indicated as “Test 2” shows the result of washing performed on thesame condition with “Test 1” while the jig 20 is used through the firstto fourth tanks. A row indicated as “Test 3” shows the result of washingperformed by increasing the output from the ultrasonic wave generator 30on the same condition with “Test 1.” A row indicated as “Test 4” showsthe result of washing performed by increasing the output from theultrasonic wave generator 30 on the same condition with “Test 2.” Everyone of the tests are made with one hundred material rings C2 and washingwith pure water to compare the washing effect.

According to the table, under the condition indicated in “Comparativeexample,” the washing effect is graded low as ninth with regard to theresin dust. On the other hand, the washing result of “Test 1” is gradedas a rank 4, “Test 2” is graded as 2, “Test 3” is graded as 1, and “Test4” is graded as 1. The rank 1 of the washing effect means that nonitriding failure is confirmed in the endless metal ring 110. In otherwords, the washing effect is improved by the washing method for theendless metal ring 110 (the material ring C2) according to the firstembodiment in which the output of the ultrasonic wave generator 30 isincreased from 8 w/L to 24 w/l, and the ring C2 is rotated and washed bythe washing jig 20. As a result, the number of the washing tanks 40 canbe reduced. Accordingly, a lead time for manufacturing the endless metalring 110 is shortened, thus reducing the manufacturing cost. Further, itis possible to contribute to extending the life expectancy of the CVTring 100.

Next, a second embodiment of the present invention is explained withreference to the accompanying drawings. A configuration is similar tothe first embodiment except a resin removal step pr6, and therefore onlythe different features are explained.

FIG. 12 is a schematic plan view of a washing device according to thesecond embodiment. FIG. 13 is a schematic perspective view of thewashing device. In the second embodiment, a carbon tetrachloridesolution is used for washing the endless metal ring 110 (the materialring C2). The washing tank 40 shown in FIG. 12 as a first tank is filledwith the carbon tetrachloride solution to wash the endless metal ring110 (the material ring C2). In washing, the material ring C2 may be heldby the washing jig 20 and rotated as necessary. Further, the ultrasonicwave generator 30 is also provided in the washing tank 40. Anotherwashing tank 40 as a second tank shown in FIG. 12 is filled with purewater and the ultrasonic washing is performed by the ultrasonic wavegenerator 30 as similar to the first tank. The ultrasonic washing isthus performed by the ultrasonic wave generator 30 while the materialring C2 is soaked in a decomposition-removal liquid in order to dissolveand remove the resin adhered to the endless metal ring 110 surface. Aslong as the solution used for washing is the one capable of dissolvingand removing the resin, the solution is not limited to the carbontetrachloride solution and other decomposition-removal liquid capable ofdissolving and removing the resin may be used.

Next, a third embodiment of the present invention is explained withreference to the accompanying drawings. A configuration is similar tothe first embodiment except a resin removal step pr6, and therefore onlythe different features are explained.

FIG. 14 is a perspective view showing a washing image of an endlessmetal ring in the third embodiment. The third embodiment is configuredsuch that the surface of the endless metal ring 110 (the material ringC2) is washed away by high-pressure washing. An inner surface washingnozzle 70 is provided inside the washing tank 40 of the washing device10 and an outer surface washing nozzle 71 is provided to be directed toan outer circumferential surface so that the endless metal ring 110surface is washed with the pressure of at least about some tens of MPa.As an alternative, the surface of the material ring C2 may be washed byemploying the method of washing at large flow rate with the pressure ofabout some tens to some hundreds of L/min. In this case, the washingtank 40 does not have to be provided with the ultrasonic wave generator30, and it is possible to remove the resin adhered to the surface of thematerial ring C2 by washing outer and inner circumferential surfaces ofthe endless metal ring 110 with the washing liquid such as pure watersprayed from the nozzles.

From the above mentioned test results, it is confirmed that washing withthe washing liquid at high temperature is also effective, and therefore,it is possible to remove the resin from the endless material ring C2surface by steam-washing the material ring C2 surface by the samenozzles. Thus, by washing the material ring C2 surface with a fluid, itis possible in the resin removal step pr6 to wash away particles of theresin media that adhered to the material ring C2 surface in the barrelpolishing step pr5.

According to the washing device 10 and the washing method of the secondor the third embodiment, the same effect as the first embodiment can beobtained, and it is possible to reduce the nitriding failure of theendless metal ring 110 as a result. Specifically, providing the resinremoval step pr6 for removing the resin dust which is considered toadhere to the endless metal ring 110 surface can realize great reductionin the nitriding failure of the endless metal ring 110.

The present invention is illustrated in accordance with the embodiments,but the invention is not limited to the above mentioned embodiments andmay be appropriately modified with its part of configuration withoutdeparting from the scope of the invention. For example, themanufacturing steps of the endless metal ring 110 are illustrated inFIG. 3, but the steps may be increased or reduced and may be replacedwith its order as long as the resin removal step pr6 is performed afterthe barrel polishing step pr5, which is performed after the cylindricalbody cutting step pr4 for cutting the cylindrical body C1, and beforethe second solutionizing step pr8. As mentioned above, it is preferablethat the resin removal step pr6 is performed before the rolling steppr7, but even in a case that the resin removal step pr6 is performedafter the rolling step pr7, for example, the resin removal effect can beexpected to a certain degree.

The shape of the CVT ring 100 is also only an example for illustration,and the present invention may be applied to a CVT ring in which a shapeof the element 102 is different from that of the present invention ascorresponding to the laminating number of the laminated rings 104.Further, the shape and others of the washing jig 20 may also bemodified. In modifying, it is preferable to configure the flame of thewashing jig 20 as thin to reduce a portion of the flame that covers thematerial ring C2 to the most extent so that the ultrasonic wavegenerated from the ultrasonic wave generator 30 is not interrupted.

REFERENCE SIGNS LIST

-   -   10 Washing device    -   20 Washing jig    -   21 Jig    -   30 Ultrasonic wave generator    -   40 Washing tank    -   100 CVT ring    -   102 Element    -   104 Laminated ring    -   110 Endless metal ring    -   116 Groove

The invention claimed is:
 1. An endless metal ring resin removal deviceconfigured to wash and hold an endless metal ring, the endless metalring resin removal device comprising: a holding tool for holding theendless metal ring; a rotation mechanism configured to rotate theendless metal ring in a circumferential direction of the endless metalring with the holding tool; a washing tank filled with a liquid forultrasonic washing of the endless metal ring; an ultrasonic wavegenerator for performing the ultrasonic washing; and an outer surfacewashing nozzle facing an outer surface of the endless metal ring forwashing the outer surface of the endless metal ring, and an innersurface washing nozzle facing an inner surface of the endless metal ringfor washing the inner surface of the endless metal ring, wherein theouter surface washing nozzle and the inner surface washing nozzle areplaced to face each other with the endless metal ring held therebetween,and a portion of the inner surface washing nozzle is placed inside theholding tool, wherein the holding tool is a basket made of wire, andwherein a part of the endless metal ring held in the holding toolprotrudes from the holding tool.
 2. The endless metal ring resin removaldevice according to claim 1, wherein the ultrasonic wave generator isoperated while the rotation mechanism rotates the endless metal ring inthe circumferential direction to remove resin having adhered to asurface of the endless metal ring.
 3. The endless metal ring resinremoval device according to claim 1, wherein the basket includes a firstlayer including a first plurality of slots and a second layer includinga second plurality of slots, the second layer being disposed above thefirst layer, and the first plurality of slots and the second pluralityof slots being aligned with each other.